Synthesis and Hydration of High Reactive Brownmillerites Ca2(Fe2−X Al x )O5

The phase forming of Brownmillerites by using well homogenized raw materials is studied. The investigations show, that iron-rich brownmillerites occur after a sintering temperature of 700°C (2 h). Alumina-rich phases were built between 800 and 1000°C (2 h). Using a conventional solid state reaction several sintering steps at 1250°C are necessary. Additionally, it could be shown that iron-rich brownmillerites were stabilized at low sintering temperatures (700°C (2 h)) in the high temperature modification (Space group:

I

2

mb

). Calorimetric studies show that alumina-rich brownmillerites are more reactive by using a constant sintering temperature of 1000°C (2 h) for all brownmillerites. However,the reactivity of iron-rich brownmillerites can be increased enormously if they were produced at lower sintering temperatures. Studies of the hydration products showed that solid solutions of [Ca

4

(Al

Y

;Fe

2−

Y

)(OH)

12

]

2+

[2(OH)∙12H

2

O]

2−

are possible.